Remove navLinkId property from feature registration

[legrego]

The Legacy Platform required the feature registration to have a distinct navLinkId property, which features had to register. This was typically the same as the application id, but was not always the case.
A notable exception were the kibana apps, which had multiple UI features within the same UI app. This generated nav link ids similar to kibana:discover, kibana:visualize and kibana:dashboards. Now that we are splitting these out into their own discrete plugins (see #63443), we can remove this extraneous property from feature registration.

Once this is removed, we should be able to populate the navLinks UI Capability property based on the registered application ids alone.

[elasticmachine]

Pinging @elastic/kibana-security (Team:Security)